Question : issues with OWA

I am getting this error message when trying to access the OWA

Exchange Active Directory Topology Service on server localhost cannot be contacted via RPC interface. Error 0x5.

The OWA just stopped working the other day and can't figure out what could have stopped it.  The server is set up very generic so if someone could assist me with that would be great.

I have people that are rely on this and need this back up and running.

Answer : issues with OWA

Check services RPC, MSExchange AD Topology, IIS Admin and WWW in started state. If possible please re-start them sequentially.

Check for events in application logs.
Check for errors in IIS console - do you find any red X on virtual directories.
Please have Exchange Best Practice Analyzer tool run in health check mode.